1. Field
One embodiment of the invention relates to a communication device that transmits a video and audio signal and a data signal via wireless communication.
2. Description of the Related Art
The IEEE 802.15 Working Group is pursuing standardization of wireless communication technology using 60 GHz band. This wireless communication technology is aimed at a wireless personal area network (WPAN), which is a wireless network having a coverage range of up to 10 m. The wireless communication technology enables gigabit-order wireless transmission using a wide band through a conventional wireless large area network (LAN) or Bluetooth. Thus, without via existing wired communication capable of transmitting a video/audio signal at high speed, such as a high definition multimedia interface (HDMI), a video/audio signal can be transmitted wirelessly.
For example, Japanese Patent Application Publication (KOKAI) No. 2008-35517 discloses a conventional technology for transmitting a video/audio signal wirelessly. According to the conventional technology, a system transmits/receives a video signal wirelessly according to the HDMI standard. Especially, by transmitting/receiving setting information for a display module wirelessly, the setting information of the display module can be read at higher speed.
On the other hand, in recent years, the HDMI standard has been being standardized to enable data communication in addition to video/audio signal transmission. The wireless communication technology described above enables not only wireless transmission of a video/audio signal but also wireless data communication over, for example, an Internet protocol (IP) network if it is one-to-one communication between wireless communication devices due to the high directivity.
Via wired communication, video/audio communication and data communication can be performed simultaneously through a single cable. On the other hand, via wireless communication, it is often difficult to perform both video/audio communication and data communication at the same time for the following reasons. (1) Video equipment cannot recognize that data communication cannot be supported in a wireless section. (2) Since a video signal requires many bands, simultaneous video/audio communication and data communication degrade video quality. (3) A band may not be ensured for data communication in a wireless section. (4) If a millimeter wave band with a wide tuning range is used to further perform data communication, when a plurality of wireless communication devices and a plurality of wireless links exist, it is not suitable for data communication because of the high directivity. Besides, the use of a plurality of wireless communication systems makes it complicated to establish a secure connection.